STORY ARCHIVE

Monsoon Fire

Australia is the most flammable continent on earth. Our trees burn like no others. From Australia to the Territory, they burn, burn, burn. Why? That’s one of the fundamental unanswered questions of our history – how did Australia become so fire prone. And it’s a story that one man, ecologist David Bowman, has made it his mission to unravel. Now, he’s come up with a suggestion so radical, it’s upsetting most of his colleagues. David now claims the ancient spark that lit our continents’ fires wasn’t the arrival of the Aborigines, nor the drying climate. The secret to our flammability, he says, lies deep in Australia’s north. But if he’s right, it overturns everything we thought we knew about our ancient pact with fire.

TRANSCRIPT

Narration: In 1836, Charles Darwin’s great round the world voyage brought him to Australia. He was struck by a uniquely Australian scar on the landscape – FIRE.

Actor Darwin V/O: In the whole country I scarcely saw a place, without the marks of fire; whether these may be more or less recent, whether the stumps are more or less black, is the greatest change.

Narration: It took over one hundred years till scientists began to ask what started the fires, and why our trees burn like no others. From Tasmania to the Territory, they burn, burn, and burn.

V/O: We’re a flammable continent. It’s a burning continent and why that should be the case, that story to me is one of the great stories.

Narration: Ecologist David Bowman is determined to revolutionise the story of why this is such a fiery continent. He’s annoyed about the popularity of the idea that it was Aborigines who first set Australia on fire.

Dr David Bowman: That’s compressing I think a very rich and complicated evolutionary story in saying that the first Australians triggered this huge fire cycle. I think what happened is that the first Australians came to a continent, which was on fire.

Narration: But David’s struggled to piece together evidence for his theory, that the fires began long before humans arrived. Then, while walking through his beloved Northern Territory savanna, the incredible biodiversity set him thinking.

Dr David Bowman: Well this landscape is the representation of evolution at its very best. That you’ve got a vegetation type, which is adapted to a very extreme alternation of a wet season and a dry season.

Narration: The evidence he needed was in the spectacular seasons of the top end of Australia. Every year, a six-month long dry season creates tinderbox conditions. Before the wet season rains arrive, dry lightning storms roll across the savannah.

Dr David Bowman: So the eureka moment was hey – This is where the lightning is. This is the most lightning prone place on earth. This is it. We’ve got a dry season, which is characteristic of the monsoonal climate and then we’ve got lightning. That’s got to equal fire.

Narration: Everyone knows that lightening starts fires. But monsoon lightning comes to the same place with the same incredible intensity every year. His revolutionary theory is that this was the force required to kick start a massive ecological change. Crucial to that change were the eucalypts. They used fire to become a predator plant. With leaves and bark are full of flammable oils; they spread the fire, killing off less hardy trees. Replacing them with their own.

Starting from the north the eucalypts too over. The rainforests that once dominated Australia until somewhere between 20 and 2 million years ago were almost wiped out.

Dr David Bowman: The fires which were started by the onset of the monsoon millions and millions of years ago have ultimately come to create the whole of the Australian landscapes and the vegetation and the animals and the plants. Everything, which we love about Australia I think initially this is the birth place, this is where it all began.

Narration: But David’s bold idea is scientific heresy to experts down south.

Professor Peter Kershaw: David is not right. At least the evidence – there’s no evidence that he’s right.

Narration: Fossils and deep earth cores are the stock in trade of Professor Peter Kershaw, an old sparring partner of David’s. While he admits the fossil record is sparse, Peter says what evidence there is doesn’t point north to the monsoon- it points south.

Professor Peter Kershaw: This is one section of a 40 metre long core from an old volcanic lake in the western uplands of Victoria. It dates to about 2 million years ago. It’s important because this actually shows the transition of the rainforest vegetation that dominated Australian vegetation for millions of years to the vegetation that dominates it today.

Narration: Based on these records, Peter favours an alternative story that is supported by most scientists. In this model, the trigger for Australia’s fire ecology was climate change. It began 30 million years ago, when the climate in Australia began drying out. The dry started in the south of the continent and spread north.

According to Peter, the drought tolerant eucalypts followed in the same direction. With them came an increase in fires. But back in the northern territory, David Bowman says the sparse fossil record doesn’t prove or disprove either story. So now, he’s out looking for more evidence to back his case. He believes he’s found it in DNA .He says the DNA of the top end Eucalypts is the oldest in Australia – it could support his idea they took over from the north.

Dr David Bowman: Yes, these trees particularly the dominants here, the stringy bark is a very primitive eucalypt on its DNA. When you make the family trees they come out to be the ancestral sort.

Narration: And now he’ s searching even further left of field. He hopes to date the arrival of the monsoon and show that it is ancient enough to have sparked Australia’s fire regime. He’ll get a date by mapping a DNA family tree of monsoon-adapted plants and animals, like these magnetic termites.

Their mounds are all perfectly aligned – a design feature that maintains near constant temperature despite the extremes of wet and dry seasons.

Dr David Bowman: I mean these things are pretty seriously strange. Some of these things are three or four metres tall. You’re talking about a blind social insect constructing these enormous things. To me that speaks of antiquity, of a huge amount of time and the key point to that is a huge amount of time for lightening to be in the environment to create the flammable Australia we all have to learn to live with.

Narration: But the DNA of these amazing creatures are unlikely to convince David’s critics. The dating techniques just aren’t accurate enough. That doesn’t deter David.

Dr David Bowman: I’m in the business of wearing down all the critics. I’m in the business of accumulating so much evidence that eventually someone else is going to have to re-interpret that evidence to come up with a better explanation and I don’t think they’re going to be able to do it.

Narration: Whichever version of events eventually wins out, all the players agree on one thing: There’s now an urgent need finally to come to grips with the ancient roots of Australia’s fires.

GRAB: I mean the general thing you can get out of this is that, fire creates vegetation which promotes more fire. The more you fire the vegetation, the more fire promoting it’s going to be.

Dr David Bowman: I’m very confident that if we keep chipping away at this enormously complicated problem we’re going to end up with an entirely new way of thinking about the evolution of flammability in Australia and help Australians ultimately change their way of life to adapt to this fiery, dry, ancient and beautiful land.